Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 211533 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 1033 AM EST SUN DEC 21 2014 .SYNOPSIS... HIGH PRESSURE MOVES ACROSS THE AREA TODAY...THEN OFF THE COAST TONIGHT. LOW PRESSURE MOVES NORTHEAST OUT OF THE GULF OF MEXICO AND UP ALONG THE CAROLINA COAST MONDAY INTO TUESDAY. A STRONG COLD FRONT WILL CROSS THE AREA WEDNESDAY NIGHT. HIGH PRESSURE RETURNS BY CHRISTMAS DAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LATEST ANALYSIS DEPICTS ~1029 MB SFC HIGH PRESSURE CENTERED OVER DE/MD/ERN VA...WITH A TROUGH OF LOW PRESSURE FROM THE ERN GULF OF MEXICO TO A POSITION OFF THE SC COAST. SKIES ARE MOSTLY CLOUDY OVER THE LOCAL AREA (EARLIER CLEAR SKIES ACRS NE NC HAVE SINCE CLOUDED OVER). LOOKING AT SATELLITE AND 12Z SOUNDINGS AS WELL AS BUFKIT FORECAST SOUNDINGS...THINK SKIES WILL STAY MAINLY CLOUDY THROUGH AT LEAST 18Z...WITH PARTIAL CLEARING LATE IN THE AFTN. HAVE ADJUSTED GRIDS TO GO A LITTLE MORE PESSIMISTIC ON THE CLOUD COVER TO ACCOUNT FOR THIS. LITTLE CHANGE NEEDED TO TEMPERATURES...HIGHS AVG AROUND 40 F ON THE ERN SHORE TO THE UPPER 40S OVER SOUTH CENTRAL VA AND NE NC. && .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/... DRY THIS EVENING. CLOUDS QUICKLY THICKEN S-N LATE EVE AND EARLY MORNING IN RESPONSE TO LOW PRES MOVG NE FROM GOM. TRICKY PART OF FCST WILL BE HOW FAST PCPN OVERSPREADS THE FA AND WHAT FORM P-TYPE WILL BE OVR THE PIEDMONT AS IN-SITU WEDGE DVLPS. DESPITE SOME TIMING DIFFERENCES LTST MODELS IN GNRL AGREEMENT THAT PCPN OVERSPREADS THE AREA S-N BTWN 06Z-12Z. LL THICKNESSES WARM ENUF FOR LIQUID PCPN E OF I95 BUT REMAIN MARGINAL W OF I95. BUFKIT SNDGS CONT TO SHOW A NARROW LAYER OF BLO FREEZING SFC TMPS THRU 15Z OR SO ACROSS THE PIEDMONT. THNK P-TYPE WILL START OFF AS A FEW HRS OF SLEET W OF I95 AND N OF RT 460 LATE TONIGHT DUE TO EVAP COOLING WITH TMPS NEAR FREEZING. MAY EVEN SEE SOME WET SNOWFLAKES OVER CNTYS NW OF RIC...BUT NOT SGNFCNT ENUF TO MENTION IN FCST ATTM. QPF LOOKS MINIMAL THRU 12Z...SO ABT THE ONLY ACTION NEEDED AT THIS POINT IS A MENTION IN HWO. RAIN SRN CNTYS. MIN TMPS MAY LIKELY OCCUR IN THE EVENING WITH STDY READINGS AFTR MIDNITE. LOWS U20S-M30S. WEDGE BEGINS TO WEAKEN MON MORNING AS HIGH PRES MOVES INTO ERN CANADA. THE NORMALLY COLDER CNTYS WILL LIKELY STAY NEAR 32 DEGREES THRU 15Z OR SO AS THE PCPN OVERSPREADS THE ENTIRE FA. EXPECT A QUICK TRANSITION OVER TO ALL RAIN MOST AREAS JUST AFTR 12Z EXCEPT FOR LOUISA/FLUVANNA/ WRN GOOCHLAND/NRN CUMBERLAND CNTYS WHERE A PERIOD OF MIXED SLEET/FZ RAIN SHUD CONT THRU AT LEAST 15Z BEFORE TMPS INCH ABV 32 F. THESE ARE THE AREAS WHERE AN ADVISORY MAY BE NEEDED MON MORNING FOR MINIMAL IMPACT AS TMPS HOVER ARND 32 F. AREAS FROM CAROLINE/NRN HALF OF NRN NECK CNTYS ON EAST TO DORCHESTER/WICOMICO MD MAY START OFF AS A RAIN/SLEET MIX AT THEN QUICKLY GO OVR TO RAIN. RAIN THEN BECOMES WIDESPREAD MON AFTRN AS THE BULK OF LIFT/MSTR TRACKS ACROSS THE FA. A RATHER COLD RAIN AS TMPS STRUGGLE TO GET OUT OF THE 30S PIEDMONT...40-45 EAST TOWARD THE ERN SHORE & SERN CHES BAY... M40S-L50S SERN VA/NC. LOW PRESSURE PROGGED TO LIFT NE ALONG THE CAROLINA COAST MONDAY NIGHT WITH STDYST PCPN ENDING SW-NE BY 06Z. SNDGS INDCTG ENUF MSTR FOR LGT RAIN / DRIZZLE THRU THE OVRNITE HRS. TMPS STDY IN THE M30S NW TO M40S SE. QPF 1/4 TO 1/2 IN. MID-LEVEL RIDGING BRIEFLY BUILDS INTO THE REGION TUESDAY. HOWEVER... MOIST EASTERLY FLOW WILL PREVAIL. KEPT LOW CHC (30%) POPS THRU THE DAY ALTHROUGH SOME DRIZZLE MAY LINGER THROUGH THE MORNING HRS. BIG TMP DIFFERENCES SEEN IN MOS DATA WHERE NAM IS SOME 5-10 DEGREES COLDER THAN THE GFS. GIVEN MODELS MAINTAIN AN ERLY SFC FLOW...WILL SPLIT THE DIFFERENCE FOR NOW AND GO WITH HIGHS FROM THE M-U40S OVR THE PIEDMONT TO M-U50S CSTL AREAS. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... A COASTAL LOW JUST OFF THE MID ATLANTIC COAST CONTINUE TO WASH OUT TUE NIGHT AS A WARM FRONT STARTS TO LIFT NORTH THROUGH THE REGION. MEANWHILE...A VERY STRONG AND VIGOROUS SFC LOW DEEPENS OVER THE OH/TN VALLEYS AND PUSHES A STRONG COLD FRONT TWD THE AREA. INITIAL PUSH OF STRATIFORM PRECIPITATION ASSOCIATED WITH THE WARM FRONT TUE NIGHT WILL LIKELY GIVE WAY TO MORE SHOWERY PRECIPITATION AS THE MID ATLANTIC REGION BECOMES WARM-SECTORED AHEAD OF THE APPROACHING COLD FRONT. THE SFC PRESSURE GRADIENT TIGHTENS SIGNIFICANTLY ON WED AS THE PARENT LOW DEEPENS OVER THE GREAT LAKES AND A STRONG JET STREAK (90-150 KT) NOSES INTO THE REGION FROM THE SSW. HIGHS SHOULD RANGE FROM 60-65 NW AND MD/VA LOWER EASTERN SHORE TO 65-69 FROM ROUGHLY RICHMOND TO SE VA/NE NC. IN ADDITION TO DEWPOINTS APPROACHING 60 DEGREES ACROSS THE SERN HALF OF THE CWA...A THETA-E RIDGE IS EXPECTED TO SURGE NWD ALONG THE SE WED MORNING INTO THE SRN MID ATLANTIC COAST BY WED AFTN/EVENING. THE COMBINATION OF THESE FEATURES/CONVECTIVE PARAMETERS MEANS THAT A SLIGHT CHANCE FOR THUNDERSTORMS HAS BEEN ADDED TO THE FORECAST ACROSS SE VA AND NE NC DURING THE AFTN/EARLY EVENING HOURS. THE FRONT EXITS THE REGION LATE WED NIGHT AND PRECIP WILL TAPER OFF FROM WEST TO EAST...COMING TO AN END EARLY THU MORNING. THE UPPER TROUGH ASSOCIATED WITH THE GREAT LAKES SFC LOW SWINGS THROUGH THE REGION LATE WED NIGHT THROUGH THU AFTN. UPPER LEVEL INSTABILITY AND ABUNDANT SFC MOISTURE FROM RECENT PRECIPITATION SHOULD KEEP SCT-BKN CUMULUS OVER THE AREA THROUGH THE DAY ON THU. CAA OCCURRING BEHIND THE COLD FRONT AND A CONTINUED TIGHT SFC PRESSURE GRADIENT WILL RESULT IN GUSTY WSW WINDS OF 20-25MPH WITH GUSTS AROUND 35MPH...AND SHOULD BE FAIRLY UNIFORM ACROSS THE REGION. THE GUSTY WINDS SHOULD DECOUPLE BY THU EVENING. OVERALL CONDITIONS FRI THROUGH THE WEEKEND SHOULD BE DRY. A LEE TROUGH FORMS ACROSS THE AREA ON FRI AND A WEAK CAD WEDGE DEVELOPS. THE PRESSURE GRADIENT RELAXES BRIEFLY FRI/FRI NIGHT AS HIGH PRESSURE BUILDING OVER THE SE STATES EXTENDS UP INTO THE MID ATLANTIC REGION. MEANWHILE...A BROAD UPPER TROUGH PUSHES A DRY COLD FRONT ACROSS THE REGION ON SAT WHICH WILL USHER MUCH COLDER 850MB TEMPS OVER THE AREA (-5 TO -15C). CAA AND A RE-TIGHTENING OF THE SFC PRESSURE GRADIENT WILL BRING A RETURN TO BREEZY SW WINDS ON SAT AND BREEZY NW WINDS ON SUN BEHIND THE NEXT COLD FRONTAL PASSAGE. && .AVIATION /16Z SUNDAY THROUGH THURSDAY/... VFR CONDITIONS AND LIGHT WINDS EXPECTED TO CONTINUE THROUGH THE 12Z TAF PERIOD. BKN-OVC CLOUDS AROUND 7K FT WILL SLOWLY ERODE THROUGH LATE MORNING/EARLY AFTN. NEXT BATCH OF PCPN WILL BEGIN TO ARRIVE FROM SOUTH TO NORTH EARLY MON MORNING. OUTLOOK...A SERIES OF LOW PRESSURE SYSTEMS AND COMPLEX FRONTAL BOUNDARIES WILL BRING CHANCES FOR RAIN AND PERIODS OF LOW CEILINGS AND VISIBILITIES MONDAY THROUGH WEDNESDAY. A COLD FRONT PASSES THROUGH WEDNESDAY NIGHT WITH VFR CONDS AND DRY WEATHER THURSDAY. && .MARINE... N-NE WINDS AOB 10 KT WILL PREVAIL TODAY WITH HIGH PRESSURE IN PLACE. WINDS TURN MORE EASTERLY TONIGHT AND INCREASE TO 10-15 KT MOST AREAS AS LOW PRESSURE ORGANIZING OFF THE SOUTHEAST COAST SLOWLY PUSHES NORTH. THE SFC LOW CONTINUES TO MOVE NORTHEAST OF THE NC COAST ON MONDAY...BUT WEAKENS BY LATE MONDAY/MONDAY NIGHT. WINDS WILL GENERALLY REMAIN E-NE AOB 15 KT ALL WATERS DURING THIS TIME...BUT TENDING TO BECOME MORE NORTHERLY AOB 10 KT BY EARLY TUES MORNING. LATEST GUIDANCE INDICATES POTENTIAL FOR SEAS TO BUILD TO AROUND 5 FT OUT 20 NM LATE MON/MON EVE ACROSS THE SOUTHERN COASTAL WATERS. CONFIDENCE NOT HIGH ENOUGH TO ISSUE A 3RD PERIOD SCA ATTM. LIGHT NW WINDS EXPECTED TUES AS HIGH PRESSURE REMAINS IN PLACE OVER THE MID-ATLANTIC...AND THE NEXT LOW PRESSURE SYSTEM ORGANIZES OVER THE DEEP SOUTH. WINDS TURN E-SE TUESDAY NIGHT AND GRADUALLY BEGIN TO INCREASE AS A WARM FRONT LIFTS NORTH THROUGH THE AREA. A STRONG COLD FRONT APPROACHES THE WATERS FROM THE WEST ON WEDNESDAY WITH WINDS BECOMING SOUTHERLY AND INCREASING TO SCA THRESHOLDS (SAVE THE RIVERS). THE FRONT QUICKLY SWEEPS THROUGH THE AREA WED NIGHT AND OFFSHORE EARLY THURSDAY. WINDS REMAIN ABOVE SCA LEVELS THRU LATE THURSDAY WHILE BECOMING SW THEN W. HIGH PRESSURE RETURNS THU NIGHT INTO THE START OF NEXT WEEKEND FOR IMPROVED CONDITIONS. SEAS WILL GENERALLY BUILD TO 5-7 FT ON WED BEFORE SUBSIDING AGAIN LATE THU. WAVES WILL REACH 4 FT ON THE CHES BAY. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...MPR NEAR TERM...LKB/MPR SHORT TERM...MPR LONG TERM...BMD AVIATION...JDM MARINE...JDM

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